Process for preparing multifilament yarns



United States Patent 3,264,390 PROCESS FOR LREPARHNG MULTI- FILAMENTYARNS David Tanner, Wilmington, Del., assignor to E. I. du Pont tieNemours and Company, Wilmington, Del, a corporation of Delaware NoDrawing. Filed July 15, 1963, Ser. No. 295,242 4 Claims. (Cl. 264171)This application is a contim1ation-in-part of my copending applicationSerial No. 118,291, filed June 20, 1961, now US. Patent 3,117,906.

This invention relates to a process for producing composite filamentsand more particularly to a process for producing splittable compositefilaments.

Composite filaments are well known in the art. Such filaments consist ofat least two longitudinally extending components which are usuallyarranged in an eccentric manner with respect to one another so that thediffering shrinkage propensities of the components results in theformation of a crimped fiber when the filament is appropriately treated,e.g., with hot water. Such filaments are produced by extruding thecomponents in a side-by-side or sheath-core relationship. Recently ithas been found that highly desirable fabrics may be prepared fromsideby-side multicomponent filaments which split apart to give two ormore filaments in place of each of the original filaments. Filaments ofthis type are disclosed and claimed in copending applications Serial No.118,470, filed June 20, 1961, now US. Patent 3,117,362, and Serial No.118,291, filed June 20, 1961, now US. Patent 3,117,906.

In order to obtain satisfactory operability in the processing of thefilaments after extrusion it is highly desirable that the filamentcomponents remain adhered together during the steps of drawing andpackaging of the yarn after extrusion. It is also desirable that thecomponents remain adhered together until the yarn is woven into a fabricbut that the components separate readily during the fabric finishingsteps so that extraordinary measures do not have to be taken in order toachieve substantially complete splitting of the filaments. In addition,it is sometimes desirable that the filaments do not crimp clue todifferent retractive forces when removed from the package for fabricpreparation. The components in the filament should, however, shrink to asubstantially different extent when exposed to hot aqueous liquids infabric finishing and also when subjected to higher temperatures in heatsetting procedures.

It is an object of this invention to provide an improved process forproducing multicomponent side-by-side splitta-ble filaments. Anotherobject is to provide a process for producing composite splittablefilaments having the characteristic that the components in the filamentsremain adhered together until the yarn is woven into fabric, but aresubsequently readily separated during the fabric finishing steps. Afurther object is to provide a process for producing compositesplittable filaments which do not crimp prior to fabric preparation butin which the components exhibit a substantial shrinkage differential infabric finishing. Other objects will become apparent from the detaileddiscussion which follows.

The above objects are accomplished by a process which comprisesextruding at least one polyamide component having a relative viscositymeasured after spinning of about 30 to 60 and at least one polyestercomponent having a relative viscosity measured after spinning of aboutto 24 from a spinneret orifice in side-by-side relationship to form acomposite filament, the ratio of the polyamide viscosity to thepolyester viscosity being from 1.5 to 2.5, attenuating the compositefilament by pulling it away from the orifice at a speed at least 40times the speed at which it is extruded, quenching the extrudedfilament, and drawing the filament from 2 to 8 times its originallength. Surprisingly, it has been found that by controlling the relativeviscosities of the polymer components within the specified limits, goodseparation of the components can be effected after a fabric has beenprepared, yet premature separation, i.e., separation before the fabrichas been prepared, is at a minimum. The relative viscosity of thepolyester component must be more rigidly controlled than the polyamiderelative viscosity. For example, if a third polymeric phase such as apolyalkylene ether anti-static agent is admixed with one or more of thecomponents, the relative viscosity of the polyester component must beadjusted within the range from about 23 to 30 in order to preventpremature splitting.

In carrying out the process of this invention, it is preferred that thegeneral procedure and spinning apparatus described in my copendingapplication Serial No. 118,291 may be used with the previously mentionedbeing adhered to. In a preferred process, the relative viscosity of thepolyester component is from 18 to 22 when no polymeric additive isincluded and from 23 to 27 when from 2 to 15% of a polymeric additive isincluded. Preferably, the filaments are drawn at a temperature above 100C. but below their melting point and then heated at a temperaturebetween about C. and 250 C. while being permitted to retract. By sotreating the drawn filaments, substantially straight filamentarystructures are provided. The period of heating should be sufiicient tocause a retraction in length of from 6 to 11%. Spinning speeds andattenuations within a broad range may be used. The filaments must beattenuated at least 40 times in order to prevent premature splitting;however, attenuations above about 1000 are usually unnecessary.

The expression relative viscosity as used herein signifies the ratio ofthe flow time in a viscometer of a polymer solution relative to the flowtime of the solvent by itself. Measurements of relative viscositiesgiven in the examples were made with the following solutions:

5.5 grams of polyamide in 50 ml. of formic acid at 25 C., or

2.15 grams of polyester in 20 ml. of a 7/10 mixture of trichlorophenol/phenol at 25 C.

Extrusion viscosity refers to the relative viscosity of polymer sampleswhich are taken before the spinneret assembly is put in place bycollecting molten polymer as it is pumped in separate streams to thespinneret.

The viscosities of the polyamide and polyester components in the yarnare determined as follows:

If the yarn sample has a finish on its surface, remove the finish bywashing the sample with carbon tetrachloride or other suitable solvent.

Transfer approximately 5 grams of the finish-free sample into a 250 ml.glass stoppered flask. Add ml. of 90% formic acid, and shake until thenylon is in solution (23 hrs.). The polyester will remain in suspension.Filter the formic acid solution through a coarse fritted glass funnel.The nylon solution will go through the filter and must be saved. Rinsethe sample in the funnel several times with formic acid until all thenylon is washed through. If the final washing turns cloudy upon additionof water, nylon is still present, and the above steps should berepeated. Add the washings to the nylon formic acid solution.

The sample remaining in the funnel is polyester. Rinse thoroughly withdistilled water, and dry in a vacuum oven at 60 C.usually overnight.Determine the relative viscosity as described above.

Precipitate the nylon by adding distilled water to the formic acidsolution and stirring well. Let this precipitate stand one-half hour tobe sure that precipitation is complete. Filter this preparationthrough afine fritted glass funnel and then rinse the precipitate several timeswith distilled Water. Dry the precipitated nylon in a vacuum This isaccomplished by flexing the end of the filament until it begins tosplitand then pulling the individual components apart. Next, asuflicient number of the individual component filaments are collected toprovide: a total denier for the filament bundle of about 85 (9.3 tex);The filament bundle is cut to a length of about 20 centimeters, theexact length being carefully observed. Each filament'bundle is thenboiled for 30 minutes in distilled water under a tension of 15milligrams, this tension being applied by clamping a small weight to thelower end of the filament bundle. dried and the length of the bundle isagain measured. The percentagereduction in length of the filamentsrelative to the original length is referred to as the boil-off" Afterthe boil-off shrinkage is measured, the

shrinkage. filament bundle is heated at 205 C. for 3 minutes in anm-cresol vapor bath under the same tension as used previously and thereduction in lengthof the filament bundle noted. The percentagereduction in length in the m-cresol vapor relative to the length of thebundle after the boil-off shrinkage measurement is referred :to asthermal shrinkage.

The splittability of the filaments of this invention'is determined bythe procedure given below. Samples for determination of prematuresplitting in drawn yarns are taken after reeling off to yards of yarn toremove any damaged yarn. If a single package is used to represent a yarnlot two samples at least 100 yards apart are taken. When using two ormore packages to represent a yarn lot,'one sampling from each package issuflicient.

For the determination of filament splittability .in the fabric, the yarnof this invention is woven as a filling in a conventional 7 O-deniernylon warp to form a 100 x 64 plain weave fabric. The fabric is thenscoured by boiling for 60 minutes in an aqueous solution containing 10grams per liter of Varsol (trademark for Esso Standard Oil Comp-anyspetroleum distillate), 0.5 gram per, liter of Triton X-100 (trademarkfor Roh'm'& Haas Companys alkyl-aryl polyether alcohol emulsifyingagent) and 0.5

gram per liter of trisodium phosphate. After rinsing and drying, 5 to 10yarn ends of the filling yarn are removed;

from each edge of the fabric and discarded. A single filling yarn isthen removed from each edge for measurement of splittability. Experiencewith this test indicates that 75 to 100% splitting in the test will giveexcellent, i.e., almost complete splitting when the fabric is subjectedto normal fabric finishing while 40 to 75% splitting in the test gives areasonably satisfactory level of splitting in The filament bundle isthen air:

eter stage mounted on either a microscope or a viewer such as the WilderMicroprojector; A straight piece of black tape is placed across thecenter of the view-screen. Align the upper edge of the cover glasswiththe tape edge with the right end of cover glass in the field. 1'With the micrometer stage,. move the slide vertically so that the upperedge moves 3 mm. up from the tape edge Moving the slide horizontally,count the filaments across the slide, counting right at the tape edge.Move the slide vertically so that theupper edge moves 4mm. up (7 mm..total from the tape edge) andcount as before- Repeat at 4 mm. intervalsto obtain five readings. .This can also be done using a regularmicroscope, although it is much less fatiguing and time-consuming withthe Wilder viewer.

(4) Repeat steps 1 to 3 onanother; bundle takenvery close to the firstfor a total-of 10 readings. It is possible to take 10 readings on oneslide, but results are statistically better if taken over two lengths ofyarn.

(5) Calculate splittability as follows:

(a) Average. ten readingsto obtain Nc (average hum-1 ber of filamentscounted) (b) Calculate :percent splitting spl.) according to thefollowing equation:-

Pei cent spl.-

Where For filaments which" split into only two components,

S.-1=1, and the equation becomes Percent spl. :Mg

The term spinning speed,? as used herein, refers to the. a

linear speed at which the .undraum filaments are wound into a package-after extrusion and quenching.

The expression attenuation refers to the ratio of: spinning speed to thelinear velocity of the filaments as they pass through the spinneretorifices, both speeds being in yards per minute.

The term normal fa'bric finishing. refers to procedures used in thetrade to finish polyester fabrics and includes the fabric. Less than 40%splitting in the test gives poor splittability in fabric finishing.

The degree of yarn splitting is determined on samples taken as describedabove, according to the following procedure:

(1) Cut a piece of the yarn bundle about 1.25 inches long, place itacross a 1-inch by 3-inch glass slide and add twoo-r three drops ofcedar immersion oil to soak the bundle is well spread, cover the bundlewith a 22 x 22 mm. cover glass and blot any excess oil from the edges.

(3) Count the filaments at five equally-spaced intervals.

This can be readily accomplished by means of a micromscouring, heatsetting, and bleaching. Relaxed finishing is preferable, in those stepsWhich permititu The following examples further :illustrate the-processof the present invention.

Example I Polyhexamethylene. adipamide. and polyethylene terephthalateflake are prepared in the conventionel manner.

The relative viscosities of the flake are shown in Tables I 1 to 3 whichfollow. The polymers are melted separatelyin screw melters and the meltsled separately to the holes of a spinning head of the:type shown in FIG.1 of copending application Serial No. 118,470, filed June20, 1961, nowUS. Patent 3,117,362, in which the bottom plate is providedwithY-shapedorifices. The two polymers are fed to the spinneret holesinside-by-side' relation in a ratio by weight of 37% polyamide and 63%polyester.

The cross-sectional area of each spinneret orifice is 0.145

neretand are .air quenched in the conventional manner. A

The filaments are subsequently drawn on a drawtwister uring a 100 C.draw pin and wound into a package in the conventional manner. The drawratio is shown in Table 1 below. The fiinal drawn yarn consists of 26filaments of 2.7 denier (0.3 tex) each, the polyamide component being1.0 denier (0.11 tex) and the polyester component 1.7 denier (0.2 tex).

The filaments are examined for premature splitting and splittabilityafter weaving into fabric as described previously. Results are shown inTable 1 for three yarns, designated A, B, and C, in which the relativeviscosity (RV) of the polyamide component at extrusion is progressivelyincreased while the viscosity of the polyester component is heldsubstantially constant. As can be seen, varying the polyamide viscositywithin the limits previously specified has no appreciable effect onfilament splittability.

Table 2 shows the results obtained when the extrusion viscosity of thepolyamide component is held substantially constant while the viscosityof the polyester component is lowered. As can be seen, the splittabilityof the filaments in fabric form is unsatisfactory for yarn D, yarn E issatisfactory in this respect, while yarn F exhibits excellentsplittability.

TABLE 2 l D b E F Polymer RV (66/p0lycster 34. 9/26. 6 34. 2/26. 8 34.2/21. 4 Extrusion RV (6-6/polyester 43. 6/26. 7 40. 8/22. 39. /20. 0Yarn RV (66/polyester) 40. 2/26. 1 38. 0/21. 8 38. 5/19.2 ViscosityRatio, (HS/polyester 1. 54 1. 74 2. 00 Draw Ratio 3.1 3. 2 3. 3Premature Splitting Non None None Splitting in Fabric Poor SatisfactoryExcellent Table 3 shows results obtained with yarns G, H, and I, whichare prepared as the other yarns except that the polymer is melted on agrid instead of in a screw melter. These results illustrate again thatat the higher polyester extrusion viscosity, splittability in the fabricis poor, while at the lower levels satisfactory splittability isobtained.

When yarns D through I are woven into fabric and the fabrics given arelaxed finishing treatment followed by heat setting, bleaching, anddyeing, the fabrics from yarns E, F, H, and I are found to be superiorto the other fabrics in bulk and aesthetics.

Example II Undrawn yarns I through P are prepared as described inExample I, except that an antistatic agent is added duringpolymerization to the 6-6 polymer. The antistatic agent employed ispolyethylene oxide capped with nonylphenol and containing about 30ethoxy units. This compound is added as a 30% aqueous solution to thestirred autoclave in sufficient amount to give 2.5 percent based on aweight of the final polymer. The undrawn yarn is attenuated by windingat a speed of 1500 y.p.m., which is about times the extrusion speed. Theundrawn yarn is then drawn over a hot pin at the pin temperature anddraw ratio given in Table 4. After drawing, the yarn is passed through atube about 3 inches in length and 0.25 inch in diameter where highpressure steam is jetted onto the yarn at the tube entrance to give thetemperatures shown in Table 4. The yarn is then wound into a package inthe conventional manner at a speed of 750 y.p.m.

Y-arn is removed from the package after winding to determine whether itdevelops a slight crimp due to differential retraction of the componentsor remains straight as desired. The results of this observation arenoted in Table 4 for the various yarns. Table 4 also shows the boil-offshrinkage values for the two components and the difference in shrinkagebetween the two. Likewise, the thermal shrinkage values and differencesare given. As can be seen from the results in Table 4, straightfilaments can be obtained under a number of different conditions.However, the combination of straight filaments, together with anappreciable difference in both boil-off shrinkage and thermal shrink-ageis obtained only under carefully selected conditions. Yarns N and O arethe only ones having straight filaments and a satisfactory level ofboil-off shrinkage.

TABLE 4 .T K L M N 0 P Spinning Speed 1, 500 1, 500 1, 500 1, 500 1, 5001, 200 1, 500 Relaxation, percent. 6 6 9 9 9 9 11 Relax. Temp., C 200200 150 150 200 Draw Pin Temp, C. 100 120 100 100 120 120 100 Draw Ratio2. 35 2. 35 2. 35 2. 35 2. 35 2. 8 2. 35 Yarn off Package Cr. Cr. Str.Str. Str. Str. Str. Boil-0ft Shrinkage,

6-6/po1yester, percent 13. 5/9. 4 13. 0/6. 7 9. 5/10. 5 11. 1/12. 6 10.4/7. 4 10. 4/6. 8 9. 9/8. 4 Boil 0ft Shrinkage Difference 4.1 7. 31.4 1. 5 3.0 3. 6 1. 5 Thermal Shrinkage 6-6/po1yester, percent1.1/4.1 1. 6/4. 8 1.2/3.6 1. 3/1. 1 1.2/3.4 1. 6/6. 8 1. 3/5. 6 ThermalShrinkage Difierenee 3.0 3. 2 2. 4 0.2 2. 2 5. 2 4. 3 Yarn RV(Hi/polyester 45. 5/23. 6 44. 0/23. 1 45. 5/23. 6 45. 5/23. 6 45. 5/22.8 45. 7/24. 5 45. 3/23. 2 Viscosity Ratio 6-6/ polyester 2.01 1. 90 1.931.93 1. 99 1.86 1. 91

Example III Yarns Q and R are prepared following the general procedureof Example II, except that the antistatic agent is omitted. Yarn isremoved from the package after 8 4 Example" VII Arnixture ofp-xylylenediarnine and m-xylylenediamine containing 10% of the latter,diarnine is combined with azelaic acid and polymerized. Thiscopolyamide and Winding to determine whether it crimps or remainspolyethylene terephthalate are extruded to form a comstraight. As shownin Table 5 below, yarn'Q which posite filament containing 50% of eachcomponentfolis given 9% relaxation, remains straight while y-arn.R,ilowing the procedure of Example I. The filaments are which is' givenonly 6% relaxation, crimps. The split attenuated, drawn and wound up asdescribed in Example tability of the filament is satisfactory. I. Thecopolymer. component in the filament has a rela- TABLE 5 I tiveviscosity of 43.8, while the. polyethylene terephthalate has a relativeviscosity of 19.7. When the yarn istested Q R as'previouslydescribed/thefilaments are found to split satisfactorily .in fabricform: but exhibit no premature -1 s littin 1 assets/ pines???1;221252313 was P Example VH1. Viscosity Ratio, (Hi/polyester. 2. 25 2. 22gg g z gfig z C g 2 A modified polyethylene terephthalate polymer ispre- Relaxation: Temp $6. ..j 200 200 pared as described in US. Patent3,018,272, Example I. Yam Ofi Package Straight Crimped This polymer,having a relative viscosity of 20, is ex-' truded in side-by-sidefrelation with polyhexamethylene ple IV adipamide having a relativeviscosity of 40 following .the Example IIIis repeated except that thefilament cross-- Procedure Example The filam,ents are attenuamd sectionis round. The results are substantially the same drawn Fmdwound updescnbed Example The I as found for the trilobal filament yarns Q and Rof polyemldfi component'm yam 18 found to have Example In relativeviscosity of 45.l while the polyester component Example V has a relativevlscosity of 19.2. When the yarn is tested as previously described, itis found to be satisfactory in Yams 1313, DD, EE ere P p e w" respect topremature splitting and splitting: in the fabric; the e h ProcedureExample The ahtlstahc The foregoing examples illustrate the criticalcontrol agent 18 Omltted from Yams AA and CO A shown In of processelements required to produce, the desired split- Table 6 (yarns AA andBB), when the antistat1c agent table fil t product e f f the component,p e Premature The relative viscosity of thepolyester componentin the 1splitting is seen. The efiect of the antistatic agent 1s. yam must,beheld a below v24 in order to Obtain also l y} o s g Y CC h DD whensatisfactory splitting of the filaments in the fabric. When P Sphmhg 1hthe h 1S encountered Wlth Yf CC an additive such as the antistatic agentillustrated in Ex at a Polyester VleeosltY level of but p i ample-Hisemployed, increased yarn viscosities in the I 'y When the antistaticagent is added, as in range from 2327 are desirable in order to preventprei Y at the ame viscosity level. mature splitting since such additivesincrease the tendency TABLE 6 AA BB 00 DD EE Spinning Speed 1,200 1, 2001, 200 1, 200 1, 200 Antistatie agent, percent None 2. 5 None 2. 5 2. 5Polymer RV (6-6/polyester) 36. 7/22. 9 40. 5/22. 3 45. 4/28. 4 46. 0/28.2 40. 9/25.8 Yarn RV (6-6/polyester) 41.0/1s.3 43.4/20.1 49.1/26.2 51.2/26.4 47.5/23.9 Viscosity Ratio, 6-6/p0lyester 2.18 2.16 1. 88 1. 94 1.99 raw Ratio 3. 2 2. 9 3. 2 2. 9 2. 9 Relaxation, percent 9.0 9. 0 9, 09. 0 9. 0 Relaxation, Temp, 175 175 175 175 175 Draw Pin Temp, O 120 120120 120 120 Premature Splitting--- None Appreciable None None NoneSplittinginFabric Excellent Excellent Poor Satisfactory Excellent ple VIof the filamentto split. In the. absence .of an additive A polymer, isPrepared in an autoclave from of this nature, the yarn viscosity ispreferably held in the aqueous solution of the salt ofbis-(para-aminocyclom of 18 22 vlscosmes be1 ow 15 lead to prematurehexyl) methane and azelaic acid. The diamine consists Sphttmg .Poor yampropemlis' of trans-trans, 25% cistrans, and 5% cis-cis iso- T Vlscosltyof the Polyamld? Componeni be mers ad usted to-the proper level relativeto the viscosity of As a viscosity stabilizer, 17.5 millimols of aceticacid the polyester. .component' Fallilre to do thls leads to i are addedfor every mol of the polyamide Salt. T118760 poor spinnability of thecomposite filament due to bendsalt solution is heated under 350 lbs/sq.in. pressure mg of the fiiamem It 1S.SueS.f.mmthe Spmneret qrlfice' fortwo hours While the temperature is raised to The polyamide zrelativevlscositles shouldbe held 1n the C. Thepressure is then reduced toatmospheric while i 3060 and.the frame of polyamlde to polysier thetemperature is raised to 315 C. and the polymer VISCPSIW h range of0mev1sheld under these conditions fior one hour. It is then 5 Cosltycombmatlons'wlthlpthese IaDgeSQmaY lead to sljme extrudedand cut toflake in the conventional manner. degree of filamenhbenllnlg but Thispalyfiler and polyethylene terephthalate are melted ad ustment of thevlscosity will eliminate this and produce and extmaed to form sidebysidecomposite filaments iis ii ie n t i ife d previously the filaments mustbe attenum Winch i i m polyester Components have ated at least 40 times,in order to prevent premature rellltvwe Yliscosltles of and respectlvelyas 70 splitting of the filament. Attenuations above about 1000 1 scribedin; Example I. The, filaments are attenuated, areusuany unnecessary andmay l d t difficulties in drawn and wound up as descr bed in Example I.When Opel-ability of, the process. The attenuation, drawing tested ykProcedures prevlhusly deserlhed, filaments temperature,'and polyesterviscosity levels should be addo not xh y Premature p g, hut split Sails.justed relative to one another as illustrated in the exfactorily in thefabric.

amples to achieve optimum splitting characteristics. Ad-

justment in these variables may also be required depending on the areaof contact between the components in the filament and upon the amountand type of additives, such as antistatic agents, delusterants, etc.,employed.

The composite filaments are preferably heated to a temperature of atleast about 80 C. before or during drawing or, while held at constantlength, subsequent to drawing to achieve the desired splittability andalso to obtain the desired shrinkage differences between the components.Heating the filaments in this manner leads to a higher shrinkage for thepolyamide component when the fabric is subjected to hot aqueoustreatments in finishing while the polyester component exhibits thehigher shrinkage in subsequent heat-setting procedures. The shrinkagedifferences lead to optimum bulk and aesthetics in the fabric and alsoact as a driving force to promote splitting.

In order to produce a filament which does not spontaneously crimp whenremoved from the package for fabric preparation, the filament must besubjected to a hot relaxation or length stabilization treatment undercarefully selected conditions of drawing and relaxation. To obtainuncrimped filaments,'while retaining a satisfactory level of boil-offand thermal shrinkage, the filaments must be drawn at a temperatureabove 100 C., preferably 115-130" C., and must subsequently be permittedto relax, sufiicient heat being applied during the relaxation step tocause a retraction in length of 6 to 11%. Where a steam treatment isemployed, temperatures in the range of 150200 C. are preferred. Otherheating means may be used, however, and if dry heat is employed asomewhat different temperature level may be required.

Suitable fiber-forming polyamides and polyesters suit able for use inthe present invention are those described in US. Patents 2,071,250,2,071,253, 2,130,523, 2,130,- 948, 2,190,770 and 2,465,319. Thepreferred group of polyamides comprises polyhexamethylene adipamide,polyhexamethylene sebacamide, poly(epsilon-caproamide). Suitablepolyesters besides polyethylene terephthalate include those containingrecurring units derived from glycols with more than two carbons in thechain, e.g., diethylene glycol, butylene glycol, decamethylene glycol,and trans-bis-1,4-(hydroxymethyl)-cyclohexane.

The yarns and fabrics prepared by the process of this invention areuseful for many purposes. The very fine deniers and variouscross-sectional shapes which can be obtained make the woven fabricsparticularly desirable substitutes for silks and fine cottons.

I claim: 1. A process for preparing a splittable composite filamentwhich comprises (1) extruding a polyamide component having a relativeviscosity, measured after extrusion, of about 30 to and a polyestercomponent having a relative viscosity, measured after extrusion, ofabout 22 to 30, the ratio of the viscosities of said polyamide andpolyester components being from 1.5 to 2.5, and

at least one of said components containing as a separate phase therein apolymeric antistatic agent,

(2) attenuating said filament by pulling it away from the orifice at aspeed at least 40 times the speed at which it is extruded, and

(3) drawing said filament from 2 to 8 times its original length.

2. The process of claim 1 wherein said filament is heated after drawingin a relaxed condition at a temperature of at least C.

3. The process of claim 1 wherein said polyamide is polyhexamethyleneadipamide and said polyester is polyethylene terephthalate.

4. The process of claim 3 wherein the relative viscosity of thepolyester is between 23 to 27.

References Cited by the Examiner UNITED STATES PATENTS 2,879,244 3/1959Coler 26033.2 2,987,797 6/1961 Breen 264-471 3,017,686 1/1962 Breen eta1. 264171 3,038,235 6/1962 Zimmerman 264-171 3,052,646 9/1962 Doggett26033.2 3,145,133 8/1964 Barton.

FOREIGN PATENTS 930,629 7/1963 Great Britain.

OTHER REFERENCES Carbowax and Polyethylene Glycols, Carbide and CarbonChem. Corp., 1946, page 4.

ALFRED L. LEAVITT, Primary Examiner.

ROBERT F. WHITE, ALEXANDER H. BROD- MERKEL, Examiners.

K. W. VERNON, Assistant Examiner.

1. A PROCESS FOR PREPARING A SPLITTABLE COMPOSITE FILAMENT WHICHCOMPRISES (1) EXTRUDING A POLYAMIDE COMPONENT HAVING A RELATIVEVISCOSITY, MEASURED AFTER EXTRUSION, OF ABOUT 30 TO 60 AND A POLYESTERCOMPONENT HAVING A RELATIVE VISCOSITY, MEASURED AFTER EXTRUSION, OFABOUT 22 TO 30, THE RATIO OF THE VISCOSITIES OF SAID POLYAMIDE ANDPOLYESTER COMPONENTS BEING FROM 1.5 TO 2.5, AND AT LEAST ONE OF SAIDCOMPONENTS CONTAINING AS A SEPARATE PHASE THEREIN A POLYMERIC ANTISTATICAGENT, (2) ATTENUATING SAID FILAMENT BY PULLING IT AWAY FROM THE ORIFICEAT A SPEED AT LEAST 40 TIMES THE SPEED AT WHICH IT IS EXTRUDED, AND (3)DRAWING SAID FILAMENT FROM 2 TO 8 TIMES ITS ORIGINAL LENGTH.